The current studies deal mainly with the synthesis and regulation of components of mammalian ribosomes. Working with high salt-washed ribosomal subunits we find several ribosomal proteins in HeLa cells which enter the ribosome very quickly, even in the absence of ribosme formation, and which are absent in the nucleolar precursor particle analyzed by two-dimensional gel electrophoresis. It does not appear that there is a significant pool of at least two of these proteins in the cell sap. The methylated amino acids from HeLa methylated ribosomal proteins have been detected. These methyl groups appear to be metabolically stable. At least one of these proteins is methylated already in the nucleolar precursor. We are currently studying the possible relationships between the methylation of various ribosomal proteins and ribosome maturation and protein synthesis. Another area of interest is the study of two homodisperse, small RNAs, which we find briefly in the cytoplasm of HeLa cells. By migration in polyacrylamide gel electrophoresis, sensitivity to camptothecin and ultraviolet irradiation, actinomycin D chases of isotope pulses, and oligonucleotide fingerprints of ribonuclease T1 digests, it is suggested that these two RNAs are precursors of the metabolically stable nuclear RNA species C and D (nomenclature of Weinberg and Penman). BIBLIOGRAPHIC REFERENCES: G. L. Eliceiri. Some Properties of the small homodisperse RNAs in the cytoplasm of HeLa cells. Biochem. Biophys. Acta, 425, 202(1976). J.P. Vandrey, C.J. Goldenberg, and G.L. Eliceiri. In vivo isotope incorporation patterns into HeLa ribosomal proteins. Biochem. Biophys. Acta, 432, 104 (1976).